Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
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-Paragraph 10
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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Fair Value Measurements (Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017	Jul. 01, 2017	Dec. 31, 2016
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	$ 31,065	$ 23,348	$ 27,148	$ 36,312
Fair value, measurements, recurring
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	31,065	23,348
Derivative financial instruments	5,146	3,354
Deferred stock-based compensation	8,901	8,885
Fair value, measurements, recurring \| Quoted prices in active markets for identical assets (Level 1)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	31,065	23,348
Derivative financial instruments	0	0
Deferred stock-based compensation	0	0
Fair value, measurements, recurring \| Significant other observable inputs (Level 2)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	0	0
Derivative financial instruments	5,146	3,354
Deferred stock-based compensation	8,901	8,885
Fair value, measurements, recurring \| Significant unobservable inputs (Level 3)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	0	0
Derivative financial instruments	0	0
Deferred stock-based compensation	0	0
Fair value, measurements, recurring \| Government securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	6,905	6,345
Fair value, measurements, recurring \| Government securities \| Quoted prices in active markets for identical assets (Level 1)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Fair value, measurements, recurring \| Government securities \| Significant other observable inputs (Level 2)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	6,905	6,345
Fair value, measurements, recurring \| Government securities \| Significant unobservable inputs (Level 3)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Fair value, measurements, recurring \| Corporate Bonds
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	5,425	6,149
Fair value, measurements, recurring \| Corporate Bonds \| Quoted prices in active markets for identical assets (Level 1)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Fair value, measurements, recurring \| Corporate Bonds \| Significant other observable inputs (Level 2)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	5,425	6,149
Fair value, measurements, recurring \| Corporate Bonds \| Significant unobservable inputs (Level 3)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Variable Rate Debt Obligation \| Fair value, measurements, recurring
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt obligations	197,000	267,500
Variable Rate Debt Obligation \| Fair value, measurements, recurring \| Quoted prices in active markets for identical assets (Level 1)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt obligations	0	0
Variable Rate Debt Obligation \| Fair value, measurements, recurring \| Significant other observable inputs (Level 2)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt obligations	197,000	267,500
Variable Rate Debt Obligation \| Fair value, measurements, recurring \| Significant unobservable inputs (Level 3)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt obligations	0	$ 0
Fixed Rate Debt Obligation \| Fair value, measurements, recurring
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt obligations	100,000
Fixed Rate Debt Obligation \| Fair value, measurements, recurring \| Quoted prices in active markets for identical assets (Level 1)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt obligations	0
Fixed Rate Debt Obligation \| Fair value, measurements, recurring \| Significant other observable inputs (Level 2)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt obligations	100,000
Fixed Rate Debt Obligation \| Fair value, measurements, recurring \| Significant unobservable inputs (Level 3)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt obligations	$ 0